Telephone system



y 1938. w. H. T. HOLDEN 2,119,211

TELEPHONE SYSTEM Filed Sept. 12, 1936 INVENTOR w H. 7. HOLDEN A T TORNE V Patented May 31, 1938 UNETED STA'iElfi PATENT OFFICE TELEPHONE SYSTEM Application September 12, 1936, Serial No. 100,404

4 Claims.

This invention relates to telephone systems and more particularly to common battery subscribers lines which terminate at a manual switchboard and are so arranged that when a 5 subscriber calls by removing his receiver from the hook a lamp is lighted before an operator as a calling signal.

In such systems it has been customary in the past to connect each line to a central battery through a double wound line relay which operates when a calling subscriber removes his receiver thereby closing a local circuit through a signal lamp usually located in the face of the switchboard. When the operator answers by inserting a cord circuit plug in the answering jack of the line a sleeve circuit is completed which operates what is known as a cut-01f relay associated with the line which disconnects the line relay and battery from the line thereby darkening the line lamp. Such an arrangement requires three distinct devices for each line, namely, a line relay, a cut-off relay and a line lamp.

An object of the present invention is to decrease the number of such devices required for a line thereby reducing the cost of the line with out lessening the efficient operation thereof.

A feature of the invention whereby the foregoing object is attained resides in the employment of what is known as a gas-filled or ionic device the function of which is to serve in the threefold capacity of a line relay, a line lamp and a cut-off relay.

The invention will be understood from the following description when read in connection with the accompanying drawing which represents a common battery subscribers line arranged in accordance with the present invention and terminating at a common battery manual switchboard.

Referring to the drawing, the apparatus within the box bounded by the broken lines, with its circuit interconnections, illustrates a common battery subscribers station I, with receiver shown off the switchhook, of the usual type, except that a special contact 2 is provided to normally ground the tip side of the line over conductor 3, for a purpose that will be hereinafter described. Station i is connectedby line conductors 4 and 5 with central office apparatus located to the right of the broken line The ionic gas-filled tube 6, located in the face of the switchboard adjacent to the answering jack 22, which is of the cold cathode, double .gap type, is so constructed that the potential necessary for ionization applied across anode element H and control element 1 or across anode element F l and cathode element 8 is much greater than the ionizing potential required across control element 1 and cathode element 8. After the control gap across elements I and 8 has bro-ken down, however, the anode gap also breaks down and ionization across the main gap is sustained, that is, across elements H and 8 at a potential only slightly greater than the breakdown potential required for the control gap. After the main or anode gap of the tube has once broken down, the control gap cannot regain control until ionization across the main gap ceases.

It has been found in practice that tube 6 can be constructed so that the control gap between elements I and 8 will break down and effect ionization of the tube when the potential connected to these elements is approximately to '70 volts and that the sustaining potential across these 5 same elements is then about 50 to 60 volts. Correspondingly, for a tube of this construction the breakdown potential between anode element H and cathode element 8 is much higherabout to volts. However, after the tube has i ionized the sustaining potential across the main gap, that is, between elements II and 8 is much less-about 70-80 volts.

Tube 6 has a three-fold function as line relay, line lamp and cut-off relay. Control element 1 is connected to the tip conductor 4, and cathode element 8, to the grounded negative pole of battery 9 through the resistance 10. Anode element H is connected through resistance l2 and the left winding of a transformer Hi to a grounded 1 alternating current ringing generator I4. Transformer i3 is constructed so that the left or primary winding is of low impedance, and the right or secondary winding of high impedance. The right winding of transformer I3 is grounded at its center point. Cathode element I5 of gasfilled tube l6, which is of the same general construction as that of tube 6, is connected to the upper terminal of aforesaid right winding and cathode element I! to the lower terminal. Anode element I8 is connected to one terminal of a night alarm ringer l9, which is connected through a key 20 to the upper terminal of the generator l4. Incoming calls which cause tube 6 to glow. as hereinafter described, are answered with cord 5 circuit 33, which is shown in abbreviated form and is of the usual common battery type, by plugging into jack 22, in which line conductors 4 and 5 terminate.

Let it be assumed that the subscriber of station I initiates a call by removing receiver 23 from its associated switchhook 24, which then assumes the position shown in the drawing, thereby opening contacts 2 to disconnect ground 25 from line conductor 4. The normal grounding of conductor 4 is to avoid the possibility of causing an improper ionization of tube 6 by leakage across line conductors 4 and 5, which might raise the potential across elements 8 and I sufliciently to falsely ionize tube 6. A circuit can now be traced from ground through auxiliary battery 26, high resistance 21, over conductor 5, through transmitter 28, switchhook contacts 29, right winding of induction coil 30 over conductor 4, through control element 1, tube 6, cathode element 8, resistance I and central oilice battery 9 to ground. The sum of the potentials of batteries 9 and 20 which in practice can be conveniently fixed at approximately 96 volts, is accordingly impressed across elements I and 8 and causes tube 6 to break down and ionize. However, due to the high resistance 21, which may be of the order of 50,000

ohms, the tube discharge current will be of low transformer I3, resistance I2, anode element II,

through tube 6, cathode element 8 and resistance I0 to grounded negative battery 9. This current will cause tube 6 to glow and attract the attention of the operator before whose position the jack 22 is located. Due to the unidirectional character of the anode element II the current passed by ringing generator I4 through the left winding of transformer I3 will be pulsating, each negative half wave being suppressed. This current will be superimposed on the current through the control gap of the tube and cause thereby a corresponding variation of the line current, which will be heard at station I as a ringing signal. The

aforesaid pulsating current will induce a potential in the right winding of transformer I 3, which will cause tube I6 to break down and ionize. As in the case of tube 6 a unidirectional pulsating current will flow from ground through generator I4, key 20 (assuming that key 2-3 is normal as shown), ringer I9, anode element I8, tube I6, cathode element 15 or IT to ground through the associated half section of the right winding of transformer I3. The current from anode element I8 will be directed to the cathode I or ll, which may be negative while anode I8 is positive. Ringer I9 now responds to the pulsating current aforesaid.

Answering the visual and audible signals before described, the operator inserts the plug SI of cord circuit 33 into jack 22. When the tip conductor of plug 3! makes contact with the tip conductor of jack 22, ground 32 is connected through the left upper winding of repeating coil 2i to line conductor 4, which reduces the potential across the elements 8 and I to such a value that tube 6 deionizes on the first occurrence of zero current from generator l4. Consequently, current ceases to flow through the left winding of transformer l3, no current is induced in the right winding and tube I6 also deionizes, silencing the ringer I9. The circuit is now ready for communication.

The description before given discussed the operation of the invention for a call originated by station I. For calls originated at the switchboard the operator will insert plug 3| into jack 22, and with a ringing key, not shown, connect ground and a source of grounded ringing current, also not shown, to line conductors 4 and 5, respectively, thereby causing ringing current to flow over conductor 5, through condenser 34, ringer 35 over conductor 3 to ground 25 through closed switchhook contacts 2. The subscriber of station I, in response to the actuation of ringer 35 now removes receiver 23 from switchhook 24. Tube 6, however, does not break down because of the ground on tip conductor 4, connected during the ringing interval and also after ringing ceases, through one of the upper windings of the repeating coil 2 I.

The description hereinbefore given, with the accompanying drawing covers only a single switchboard appearance of the subscribers line. It is to be understood, however, that other appearances may be provided, by connecting one additional tube, similar to tube 6, for each additional appearance.

For a plurality of tubes, the control elements corresponding to element 1 of tube 6 should all be connected together. Each element corresponding to element 8 should be provided with an individual resistance corresponding to resistance In and connected to the common battery 9. Each anode element II should be provided with its individual resistance I2 and connected to the upper terminal of the left winding of transformer I3 and the tip and sleeve conductors of all jacks should be multipled. When the receiver at station I is removed from its switchhook 24, all tubes will ionize and glow and the entire anode discharge current of all tubes will now pass through the left winding of common transformer I3. As soon as an operator responds by inserting the plug of a cord circuit into an associated jack all tubes will be deionized and cease to glow and the operators at other positions will know that the call has been answered. For calls outgoing to station I, a busy test terminal 38 may be provided for each jack and so arranged that when a plug is inserted into a jack associated local contacts 3'! will close and connect auxiliary battery 26 through common resistance 38 to the corresponding test terminal and all the other terminals which are connected in multiple with it. When the operator touches a test terminal with the tip of the cord circuit plug, current will flow from battery 26, through resistance 38, contacts 37 of jack 22, or corresponding contacts of another multiple jack, terminal 36 or some other corresponding multipled terminal, through the tip conductor of the cord circuit and winding of repeating coil 2| to ground, thereby causing a click in the receiver of the 'operators telephone circuit, not shown, and indicating that the line is busy.

What is claimed is:

1. In a common battery telephone system, a switchboard, a subscribers line terminating thereat, a gas-filled discharge device having two discharge paths, a source of alternating current, a central oflice battery, an auxiliary source of direct current potential, a connection across said line serially including one of said discharge paths, said central office battery, said auxiliary source and a high resistance, and a circuit serially including said second discharge path, said alternating current source and said central oifice battery, said auxiliary source of potential being connected in an aiding direction with respect to the central ofiice battery across said first discharge path, the potential of said auxiliary source being of such a value as, when added to the potential of the central office battery, to cause said first discharge path to break down and effect ionization of said device, and said discharge device being so constructed and arranged that the anode electrode of the second path will be sufli'ciently illuminated by discharge thereacross to serve as a visual signal.

2. In a common battery telephone system, a switchboard, a subscribers line terminating there'- at in a jack, a cord circuit adapted to be connected to said line through the medium of said jack, a central office battery connected in bridge of said cord circuit, a gas-filled discharge device having two discharge paths, a source of alternating current, an auxiliary source of direct current potential, a connection across said line serially including one of said discharge paths, said auxiliary source, the central ofiice battery and a high resistance, and a circuit for said second discharge path serially including said central office battery and said alternating current source, said auxiliary source of potential and said central ofiice battery in said first discharge path being connected in series aiding with respect to each other and in a reverse polarity direction across said line to the polarity of said central ofiice battery when it is connected to the line by means of said cord circuit and jack.

3. In a common battery telephone system, a line, a central office battery, a link circuit adapted to be connected to said line to connect said central ofiice battery thereacross in one polar direction, an auxiliary source of direct current, a source of alternating current, a three-element gas-filled discharge device comprising an anode, a cathode, and a control electrode, a first circuit in bridge of said line serially including said cathode, control electrode, central office battery, and auxiliary source, said battery and auxiliary source being connected in said first circuit in series aiding and in a polar direction opposed to the direction of connection of said battery to the line by said link circuit, and a second circuit including said anode, alternating current source, and that portion of the first circuit including the cathode and central oifice battery.

4. In a common battery telephone system, a line, an ionic glow discharge device associated therewith, and means, including a central office battery, an auxiliary source of direct current,

and a source of alternating current, cooperating with said line and device for causing said device to serve the three-fold purpose of a line relay, line lamp, and cut-off relay.

WILLIAM H. T. HOLDEN. 

